Over the last few decades, digital two-way radio networks have become widespread. Typically, two-way radios allow users to receive as well as transmit voice or data. To provide interoperability between various digital two-way radio systems and vendors, European Telecommunication Standards Institute (ETSI) has introduced a Digital Mobile Radio (DMR) air interface standard, which specifies various protocols used by the two-way radios at the data link layer (i.e., layer 2) of the well known seven-layer Open Systems Interconnection computer networking model, and which is described in ETSI TS (Technical Specification) 102 361-1 v1.4.5 (2007-12). Reference herein to the ETSI DMR standard includes the current version of the technical specification and all subsequent and future versions.
The ETSI DMR standard specifies a two-slot Time Division Multiple Access (TDMA) structure that transmitting and receiving devices can utilize to send voice and/or data signals. The voice and data signals are transmitted in the TDMA slots in accordance with a general burst format specified in the standard. In addition, the bursts comprising voice signals are transmitted in superframes that are 360 ms long and have six bursts that are designated with the letters “A” through “F”.
Moreover, the voice and data messages can be sent in the clear as plain information or can be encrypted and made private so that the data cannot be read or the voice cannot be heard on any device other than one that has the proper parameters needed to decrypt the messages. Accordingly, encryption and decryption (or privacy) is a way to protect communications and keep them private when sending the messages between two devices. However, in the context of this disclosure, privacy does not provide any mechanism to authenticate the devices or users or to protect the integrity of the messages, for instance, to ensure that the messages are decoded in the proper order or that all of the messages were actually received at the receiving device.
The encryption process generally comprises a transmitting device combining certain cryptographic parameters with the plain information to generate protected information that is sent to a receiving device. For encryption processes that use a cryptographic algorithm, such as ARC4, the cryptographic parameters typically include a key, the cryptographic algorithm, and an initialization vector (IV) for the algorithm. Accordingly, in order to properly decrypt the protected information, the receiving device has to know and use the same key, cryptographic algorithm, and IV that were used by the transmitting device.
To make the cryptographic parameters known to the receiving device, the transmitting device can send to the receiving device the cryptographic parameters themselves and/or encryption identifiers (IDs) that identify one or more of the cryptographic parameters. The cryptographic parameters and encryption identifiers are collectively referred to herein as encryption parameters. Thus, when referring to a set of encryption parameters, the set could include one or more cryptographic parameters only, one or more encryption identifiers only, or a combination of both cryptographic parameters and encryption identifiers. Currently, there is no method defined in the DMR standard for transporting encryption parameters.
Thus, there exists a need for a method and device for transmitting encryption parameters that can be implemented in a DMR system.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments. In addition, the description and drawings do not necessarily require the order illustrated. Device and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the various embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein. Thus, it will be appreciated that for simplicity and clarity of illustration, common and well-understood elements that are useful or necessary in a commercially feasible embodiment may not be depicted in order to facilitate a less obstructed view of these various embodiments.